1. Field of the Invention
This invention relates generally to the field of power supplies and specifically to a load-sharing redundant power system.
2. Relevant Art
Power supplies are used in many mission critical applications where it is desirable to continue to provide operating power to certain electrical and electronic systems even in the event of a utility power outage or power supply failure.
An uninterruptible power supply (UPS) system provides backup power-for the protected system from a battery source that is charged by the utility power. It is desirable to utilize an efficient connection from the battery to the load when the utility power is not available. Power management is often part of the UPS system operation.
UPSs are used in many different applications, some of which demand particular output power waveforms from the UPS. Therefore, it is advantageous for a UPS to have a configurable output waveform. It is also advantageous for the UPS to operate from a wide variety of input voltages and frequencies.
When a single UPS is used, there is still a possibility that the UPS could fail and leave the application without power. Thus, in mission critical applications, such as telecommunications, it is desirable to redundantly operate several UPSs or other power supplies connected together to provide power to the same load or system.
Such a redundant power scheme is often referred to as xe2x80x9cload sharing.xe2x80x9d If one of the power supplies operating redundantly fails or must be otherwise shutdown, the remaining redundant supply or supplies continue to supply power to the load.
Such redundant, load-sharing power supplies should have their outputs synchronized so that the desired waveform is supplied to the load and so that the power supplies do not damage one another or the load.
The present invention provides a redundant power system comprising a plurality of power supplies each connected to a common master-present bus and a common AC output bus. The plurality of power supplies each comprise an AC output connected to the common AC output bus.
Each power supply further comprises a redundant circuit for redundantly operating the power supply in cooperation with the respective redundant circuits of each of the other power supplies, the redundant circuit operating as determined by a local master/slave status as one of a master and a slave.
Each power supply further comprises arbitration logic in communication with the common master-present bus, wherein if the arbitration logic senses a master-not-present signal on the common master-present bus, then the arbitration logic sets the local master/slave status to master and transmits a master-present signal to the common master-present bus node, and wherein if the arbitration logic senses a master-present signal on the master bus and the local master/slave status is not set to master, then the arbitration logic sets the local master/slave status to slave.
According to a further aspect, the present invention provides a redundant power system comprising a plurality of power supplies each connected to a common polarity bus. The plurality of power supplies each comprises a local master/slave status settable to one of master and slave, and a synchronization circuit which reads a polarity value from the common polarity bus and if the local master/slave status is set to master, then the synchronization circuit transmits a master polarity signal to the common polarity bus. Each power supply further comprises a power section comprising an AC output and a polarity control connected to set the polarity of the AC output according to the polarity value of the common polarity bus.
According to a still further aspect, the present invention provides a redundant power system comprising a plurality of power supplies each connected to a common bias bus. The plurality of power supplies each comprises a redundant circuit for cooperation with a corresponding redundant circuit of each of the other power supplies and a power section for providing a local bias voltage. Each power supply further comprises a redundant bias circuit for contributing to a common bias voltage at the common bias bus, the redundant bias circuit providing operating power to the redundant circuit.
Each power supply further comprises a bias diode for performing a logical OR operation of the local bias voltage onto the common bias connection, wherein the redundant bias circuit is adapted to provide the operating power to the redundant circuit from the local bias voltage and to alternatively provide the operating power to the redundant circuit from the common bias connection when the local bias voltage is unavailable.
According to yet a further aspect, the present invention provides a power supply for operation in a redundant power system. The power supply comprises a power section comprising an AC output and a start-up cycle. The power supply further comprises a start-ready connection for connection to a corresponding start-ready connection of at least one other power supply. The power supply further comprises a soft-start circuit for transmitting a not-ready signal to the start-ready connection until the start-up cycle has completed, wherein the soft-start circuit disrupts the operation of the AC output until the soft-start circuit senses no not-ready signal at the start-ready connection.
According to yet a still further aspect, the present invention provides a power supply for operation in a redundant power system. The power supply comprises a power section comprising a pulse-width modulation signal and an AC output for connection to a corresponding AC output of at least, one other power supply.
The power supply further comprises an overvoltage detection circuit sensing a peak voltage level of the AC output, wherein the overvoltage detection circuit transmits an overvoltage signal if the peak voltage level exceeds a predetermined peak voltage level. The power supply further comprises a duty-cycle detection circuit sensing a duty cycle level of the pulse-width modulation signal, wherein the duty-cycle detection circuit transmits a maximum-duty-cycle signal when the duty-cycle level of the pulse-width modulation signal exceeds a predetermined maximum duty-cycle level.
The power supply further comprises an overvoltage correction circuit in communication with the overvoltage detection circuit and in communication with the duty-cycle detection circuit, wherein the overvoltage correction circuit disrupts the operation of the AC output when the overvoltage correction circuit detects both the overvoltage signal and the maximum-duty-cycle signal.